The NFL passer rating is one of the oldest composite statistics in professional sports — it dates to 1973 — and it remains both widely cited and widely misunderstood. Broadcasters quote it constantly during games. Fans use it to compare quarterbacks across generations. And yet most people who reference it couldn't tell you how it's actually calculated. The formula is specific, somewhat arbitrary, and full of structural quirks that matter enormously when you try to use it seriously.
The Four Components of Passer Rating
Passer rating is built from four independent components, each derived from a different aspect of a QB's passing performance:
- Completion percentage — catches per attempt
- Yards per attempt — passing yards divided by pass attempts
- Touchdown percentage — touchdowns per attempt
- Interception percentage — interceptions per attempt (penalizes the QB)
Each component is calculated separately, then averaged and scaled to produce a final rating between 0 and 158.3.
The Formula (Step by Step)
Each component uses a specific formula. Every component is then clamped between 0 and 2.375 — this cap is one of the formula's most significant design decisions.
a = ((Completion% / 100) / 0.3 - 1) × 0.05 × 100
→ simplified: (Cmp% - 30) × (1/20)
b = ((Yards/Attempt - 3) × 0.25)
c = (TD% / 100 / 0.05) × 0.2 × 100
→ simplified: TD% × 0.2 / 0.05 = TD% × 4
d = (0.095 - (INT% / 100)) / 0.04 × 0.2 × 100
→ simplified: 2.375 - (INT% × 25)
Each of a, b, c, d is clamped: minimum 0, maximum 2.375.
Passer Rating = ((a + b + c + d) / 6) × 100
The division by 6 and multiplication by 100 normalizes the result to a familiar 0–158.3 scale. The maximum of 158.3 occurs when all four components hit 2.375.
Worked Example: A 300-Yard Game
A quarterback completes 22 of 32 pass attempts for 295 yards, 2 touchdowns, and 0 interceptions.
Step 1: Calculate component inputs
- Completion%: 22 ÷ 32 × 100 = 68.75%
- Yards/Attempt: 295 ÷ 32 = 9.22
- TD%: 2 ÷ 32 × 100 = 6.25%
- INT%: 0 ÷ 32 × 100 = 0%
Step 2: Calculate each component
a = (68.75 - 30) / 20 = 38.75 / 20 = 1.9375
b = (9.22 - 3) × 0.25 = 6.22 × 0.25 = 1.555
c = 6.25 × 0.2 / 0.05 = 6.25 × 4 = 25 → capped at 2.375
d = 2.375 - (0 × 25) = 2.375
Step 3: Average and scale
Sum = 1.9375 + 1.555 + 2.375 + 2.375 = 8.2425
Rating = (8.2425 / 6) × 100 = 137.4
A 137.4 passer rating represents an excellent performance — completing over two-thirds of passes, throwing no interceptions, hitting the TD threshold, and exceeding 9 yards per attempt.
What's a "Good" Passer Rating?
Interpreting the number requires historical context. The NFL's league-wide passer rating has risen steadily since the 1970s, making era comparisons tricky.
| Passer Rating Range | Interpretation | Modern Season Equivalent |
|---|---|---|
| Below 60 | Poor | Backup QB territory |
| 60–79 | Below average | Starter struggling to keep job |
| 80–89 | Average / serviceable | Middle-of-the-pack starter |
| 90–99 | Good | Solid starter, playoff-caliber |
| 100–109 | Very good | Pro Bowl consideration |
| 110–119 | Excellent | MVP candidate |
| 120+ | Elite season | Top of historical leaderboards |
| 158.3 | Perfect game | Achieved ~17 times in NFL history |
The modern league average passer rating hovers around 90–92, substantially higher than the 65–72 range common in the 1970s and 1980s. Rule changes protecting quarterbacks and receivers, emphasis on passing offenses, and improved coaching have inflated ratings significantly.
Why the Formula Is Controversial
The passer rating formula has several well-documented structural flaws.
Capped components: Once a QB exceeds 77.5% completion rate, 12.5 yards per attempt, 11.875% TD rate, or throws zero interceptions, additional improvement in those areas adds nothing to the rating. A QB who completes 80% of his passes and one who completes 95% receive identical credit in the completion component.
No penalty for sacks: A sack is not an incomplete pass — it's an attempt that loses yardage, with a risk of fumble and injury. Passer rating treats every sack as if it didn't happen.
No fumble accounting: Fumbles, including those lost during scrambles, affect game outcomes significantly but contribute nothing to passer rating.
Era dependency: Because the formula was calibrated to 1971 passing statistics, what was "average" in 1973 looks like a poor performance by 2024 standards. Comparing Joe Montana's career 92.3 to Patrick Mahomes' career 106.4 requires adjusting for era — the formula doesn't do this automatically.
Doesn't distinguish context: A 20-yard screen pass and a 20-yard deep ball count identically. Fourth-quarter comeback drives and garbage-time stat padding are indistinguishable.
Alternative Metrics: QBR, EPA, CPOE
Modern analytics has produced several complementary (or competing) QB metrics.
ESPN QBR (Total Quarterback Rating): Accounts for run and pass plays, adjusts for game situation (down, distance, game score), credits plays to the QB vs receivers vs play design, and caps credit for "lucky" outcomes. Scale is 0–100, with 50 as average. More comprehensive than passer rating but proprietary and opaque.
EPA (Expected Points Added) per play: Measures how much each play increased or decreased the offense's expected point total based on field position, down, and distance. EPA per dropback is now widely considered the most predictive per-play QB metric. Available publicly from nflfastR data.
CPOE (Completion Percentage Over Expected): Measures actual completion rate versus the expected rate given the depth of target, receiver separation, and other factors. A QB with +5% CPOE is completing 5 more passes per 100 attempts than an average QB would given the same throw difficulty. Separates skill from scheme.
None of these metrics is complete on its own. A full quarterback evaluation uses passer rating as a baseline, EPA/play and CPOE for process-based assessment, and QBR or a team-context model for situational value. Passer rating's 50-year track record means it still communicates useful information quickly — its flaws matter most when making precise comparisons rather than rough-order assessments.